Jian Qingyang was defeated. When a son of Heaven appeared in an invincible form, defeating opponent after opponent, the countless amounts of praise and worship he accrued would completely collapse the moment he was defeated. People inevitably said things like "Jian Qingyang was not that great after all" in private.
A person, who accomplished nothing all his life, would be praised by others whenever he became a hero or accomplished a feat.
However, a person, who was already a top hero at his peak, would only be met with derisive ridicule after being defeated and humiliated.
People were accustomed to celebrating a failure's victory, but they could not tolerate a constant winner's failure.
Furthermore, Jian Qingyang's defeat was too tragic. He had been defeated by the Fey race, and he has lost the glory that belonged to the Human race.